How to easily identify which nodes have logic bricks attached to them in the outliner
You can run the following in the Text Editor to select all objects in the scene with a logicbrick.

import bpy

bpy.ops.object.select_all(action="DESELECT")
logicbricks = ("controllers", "sensors", "actuators")
for obj in bpy.context.scene.objects:
    if any(len(getattr(obj.game, brick_type)) for brick_type in logicbricks):
        obj.select = True
bpy.context.scene.objects.active = obj